Background. Use of a robotic tool to perform surgery introduces a risk of unexpected soft tissue damage due to the lack of tactile feedback for the surgeon. Early experience with robotics in total hip and knee replacement surgery reported having to abort the procedure in 18–34 percent of cases due to inability to complete preoperative planning, hardware and soft tissue issues, registration issues, as well as concerns over actual and potential soft tissue damage. These damages to the soft tissues resulted in significant morbidity to the patient, negating all the desired advantages of precision and reproducibility with robotic assisted surgery. The risk of soft tissue damage can be mitigated by haptic software prohibiting the cutting tip from striking vital soft tissues and by the surgeon making sure there is a clear workspace path for the cutting tool. This robotic total knee system with a semi-active haptic guided technique was approved by the FDA on 8/5/2015 and commercialized in August of 2016. One year clinical results have not been reported to date. Objective. To review an initial and consecutive series of robotic total knee arthroplasties for safety in regard to avoidance of known or delayed soft tissue injuries and the necessity to abort the robotic assisted procedure and resort to the use of conventional implantation. Report the clinical outcomes with robotic total knee replacement at or beyond one year to demonstrate satisfactory to excellent performance. Methods. The initial consecutive series of 100 robotic total knee replacements using a semi-active haptic guided system including 34 from the initial IDE series in 2014 and those performed after commercial approval beginning in 2016 were reviewed. Pre- operative planning utilizing CT determined the implant placement and boundaries and thus the limit of excursion from any part of the end effector saw tip. Self-retaining retractors were also utilized. Operative reports, 2, 6, and 12 week, and yearly follow-up visit reports were reviewed for any evidence of inadvertent injury to the medial collateral ligament, patellar tendon, or a neurovascular structure from the cutting tool. Operative notes were also reviewed to determine if the robotic procedure was partially or completely aborted due to any issue. Knee Society and Functional scores were recorded from pre-operative and yearly. Results. No cases were unable to be completed robotically. No case had evidence for acute or delayed injury to the medial collateral ligament, patellar tendon, or neurovascular structure. The average follow-up for this series was 1.54 years. Average pre- operative Knee Society and Functional Scores improved from 44.7 and 50 to 98.1 and 87.8 at one year follow-up, 93.8 and 83.1 at two year follow-up, 98.5 and 87.7 at three year follow-up, and 99 and 85 at four year follow-up. Conclusions. A semi-active haptic guided robotic system is a safe and reliable method to perform total knee replacement surgery. Preliminary short-term outcomes data shows excellent clinical and functional results

Background. There are limited previous findings detailed biomechanical properties following implantation with mechanical and kinematic alignment method in robotic total knee arthroplasty (TKA) during walking. The purpose of this study was to compare clinical and radiological outcomes between two groups and gait analysis of kinematic, and kinetic parameters during walking to identify difference between two alignment method in robotic total knee arthroplasty. Methods. Sixty patients were randomly assigned to undergo robotic-assisted TKA using either the mechanical (30 patients) or the kinematic (30 patients) alignment method. Clinical outcomes including varus and valgus laxities, ROM, HSS, KSS and WOMAC scores and radiological outcomes were evaluated. And ten age and gender matched patients of each group underwent gait analysis (Optic gait analysis system composed with 12 camera system and four force plate integrated) at minimum 5 years post-surgery. We evaluated parameters including knee varus moment and knee varus force, and find out the difference between two groups. Results. The mean follow up duration of both group was 8.1 years (mechanical method) and 8.0 years (kinematic method). Clinical outcome between two groups showed no significant difference in ROM, HSS, WOMAC, KSS pain score at last follow up. Varus and valgus laxity assessments showed no significant inter-group difference. We could not find any significant difference in mechanical alignment of the lower limb and perioperative complicatoin. In gait analysis, no significant spatiotemporal, kinematic or kinetic parameter differences including knee varus moment (mechanical=0.33, kinematic=0.16 P0.5) and knee varus force (mechanical=0.34, kinematic=0.37 P0.5) were observed between mechanical and kinematic groups. Conclusions. The results of this study show that mechanical and kinematic alignment method provide comparable clinical and radiological outcomes after robotic total knee arthroplasty in average 8 years follow-up. And no functional difference were found between two knee alignment methods during walking

Introduction. This study sought to evaluate the patient experience and short-term clinical outcomes associated with the hospital stay of patients who underwent robotic arm-assisted total knee arthroplasty (TKA). These results were compared to a cohort of patients who underwent TKA without robotic assistance performed by the same surgeon. Methods. A cohort of consecutive patients undergoing primary TKA for the diagnosis of osteoarthritis by a single fellowship trained orthopaedic surgeon over a 39-month period was identified. Patients who underwent TKA during the year this surgeon transitioned his entire knee arthroplasty practice to robotic assistance were excluded to eliminate selection bias and control for the learning curve. A final population of 538 TKAs was identified. Of these, 314 underwent TKA without robotic assistance and 224 underwent robotic arm-assisted TKA. All patients received the same prosthesis and post-operative pain protocol. Patient demographic characteristics and short-term clinical data were analyzed. Results. Robotic arm-assisted TKA was associated with shorter length of stay (2.3 versus 2.6 days, p< 0.001), a 50% reduction in morphine milligram equivalent utilization (from 213 to 105, p< 0.001), decreased visual analog scale pain score on post-op day 1 and 2 (p< 0.001), and a mean increase in procedure time of 8.2 minutes (p=0.08). There were no post-operative infections in either cohort. Additionally, there were no significant differences in rates of manipulation under anesthesia, emergency department visits, readmissions, or return to the operating room. Conclusions. This analysis corroborates existing literature suggesting that robotic arm-assisted TKA can be correlated with improved short-term clinical outcomes. This study reports on a single surgeon's experience with regard to analgesic requirements, length of stay, pain scores, and procedure time following a complete transition to robotic arm-assisted TKA. These results underscore the importance of continued evaluation of clinical outcomes as robotic arthroplasty technology continues to grow. For any figures or tables, please contact authors directly

Background. There are limited previous findings detailed biomechanical properties following implantation with mechanical and kinematic alignment method in robotic total knee arthroplasty (TKA) during walking. The purpose of this study was to compare clinical and radiological outcomes between two groups and gait analysis of kinematic, and kinetic parameters during walking to identify difference between two alignment method in robotic total knee arthroplasty. Methods. Sixty patients were randomly assigned to undergo robotic-assisted TKA using either the mechanical (30 patients) or the kinematic (30 patients) alignment method. Clinical outcomes including varus and valgus laxities, ROM, HSS, KSS and WOMAC scores and radiological outcomes were evaluated. And ten age and gender matched patients of each group underwent gait analysis (Optic gait analysis system composed with 12 camera system and four force plate integrated) at minimum 5 years post-surgery. We evaluated parameters including knee varus moment and knee varus force, and find out the difference between two groups. Results. The mean follow up duration of both groups was 8.1 years (mechanical method) and 8.0 years (kinematic method). Clinical outcome between two groups showed no significant difference in ROM, HSS, WOMAC, KSS pain score at last follow up. Varus and valgus laxity assessments showed no significant inter-group difference. We could not find any significant difference in mechanical alignment of the lower limb and perioperative complicatoin. In gait analysis, no significant spatiotemporal, kinematic or kinetic parameter differences including knee varus moment (mechanical=0.33, kinematic=0.16 P0.5) and knee varus force (mechanical=0.34, kinematic=0.37 P0.5) were observed between mechanical and kinematic groups. Conclusions. The results of this study show that mechanical and kinematic alignment method provide comparable clinical and radiological outcomes after robotic total knee arthroplasty in average 8 years follow-up. And no functional differences were found between two knee alignment methods during walking

Background. Use of a robotic tool to perform surgery introduces a risk of unexpected soft tissue damage due to the uncommon tactile feedback for the surgeon. Early experience with robotics in total hip and knee replacement surgery reported having to abort the procedure in 18–34 percent of cases due to inability to complete preoperative planning, hardware and soft tissue issues, registration issues, as well as concerns over actual and potential soft tissue damage. These can result in significant morbidity to the patient, negating all the desired advantages of precision and reproducibility with robotic assisted surgery. The risk of soft tissue damage can be mitigated by haptic software prohibiting the cutting tip from striking vital soft tissues and by the surgeon making sure there is a clear workspace path for the cutting tool. This robotic total knee system with a semi-active haptic guided technique was approved by the FDA on 8/5/2015 and commercialized in August of 2016. Two year clinical results have not been reported to date. Objective. To review an initial and consecutive series of robotic total knee arthroplasties for safety in regard to avoidance of known or delayed soft tissue injuries and the necessity to abort the using the robot to complete the procedure. Report the clinical outcomes with robotic total knee replacement at or beyond two years to demonstrate no delayed effect on expected outcome. Methods. The initial consecutive series of 65 Triathlon. TM. total knee replacements using a semi-active haptic guided system that were performed after commercialization that would be eligible for two year follow-up were reviewed. Pre-operative planning utilizing CT determined the implant placement and boundaries and thus the limit of excursion from any part of the end effector saw tip. Self-retaining retractors were also utilized. Operative reports, 2, 6, and 12 week, and yearly follow-up visit reports were reviewed for any evidence of inadvertent injury to the medial collateral ligament, patellar tendon, or a neurovascular structure from the cutting tool. Operative notes were also reviewed to determine if the robotic procedure was partially or completely aborted due to any issue. Knee Society Knee Scores (KS-KS) and Functional Scores (KS-FS) were recorded from pre-operative and yearly. Any complications were recorded. Results. 40 cases had two year follow-up. The average follow-up for this series was 1.51 years. No cases were unable to be completed robotically. No case had evidence for acute or delayed injury to the medial collateral ligament, patellar tendon, or neurovascular structure. The only complication was a revision total knee for tibial component loosening after a fall induced periprosthetic tibial fracture. Average pre-operative KS-KS and KS-FS improved from 46.9 and 52.1 to 99.2 and 88.6 at one year follow-up, 100.5 and 86.9 at two year follow-up. Conclusions. A semi-active haptic guided robotic system is a safe and reliable method to perform total knee replacement surgery. This series of initial robotic arm assisted surgery had no intraoperative or delayed soft tissue injuries. Preliminary short-term outcomes at up to two years show excellent outcomes

The preoperative prediction of gap balance after robotic total knee arthroplasty (TKA) is difficult. The purpose of this study was to evaluate the effectiveness of a new method of achieving balanced flexion-extension gaps during robotic TKA. Fifty one osteoarthritic patients undergoing cruciate retaining TKA using robotic system were included in this prospective study. Preoperative planning was based on the amount of lateral laxity in extension and flexion using varus stress radiograph. After complete milling by the robot and soft tissue balancing, intra-operative extension and flexion gaps were measured using a tensioning device. Knees were subdivided into three groups based on lateral laxities in 0° and 90° of flexion, as follows; the tight extension group (≥ 2mm smaller in extension than flexion laxity), the tight flexion group (≥ 2mm smaller in flexion than extension laxity), and the balanced group (< 2mm difference between laxities). In addition, intra-operative gap balance results were classified as acceptable (0–3mm larger in flexion than in extension), tight (larger in extension than in flexion) or loose (> 3mm larger in flexion than in extension) based on differences between extension and flexion gaps. During preoperative planning, 34 cases were allocated to the balanced group, 16 to the tight extension group and 1 case was allocated to the tight flexion group. Intra-operative gap balance was acceptable in 46 cases, 4 cases had a tight result, and one case had a loose flexion gap. We concluded that preoperative planning based on the amount of lateral laxity determined using varus stress radiographs may be useful for predicting intraoperative gap balance and help to achieve precise gap balance during robotic TKA

The introduction of robotics for total knee arthroplasty (TKA) into the operating theatre is often associated with a learning curve and is potentially associated with additional complications. The purpose of this study was to determine the learning curve of robotic-assisted (RA) TKA within a multi-surgeon team. This prospective cohort study included 83 consecutive conventional jig-based TKAs compared with 53 RA TKAs using the Robotic Surgical Assistant (ROSA) system (Zimmer Biomet, Warsaw, Indiana, USA) for knee osteoarthritis performed by three high-volume (> 100 TKA per year) orthopaedic surgeons. Baseline characteristics including age, BMI, sex and pre-operative Kellgren-Lawrence grade were well-matched between the conventional and RA TKA groups. Cumulative summation (CUSUM) analysis was used to assess learning curves for operative times for each surgeon. Peri-operative and delayed complications were reviewed. The CUSUM analysis for operative time demonstrated an inflexion point after 5, 6 and 15 cases for each of the three surgeons, or 8.7 cases on average. There were no significant differences (p = 0.53) in operative times between the RA TKA learning (before inflexion point) and proficiency (after inflexion point) phases. Similarly, the operative times of the RA TKA group did not differ significantly (p = 0.92) from the conventional TKA group. There was no discernible learning curve for the accuracy of component planning using the RA TKA system. The average length of post-operative follow-up was 21.3 ± 9.0 months. There was no significant difference (p > 0.99) in post-operative complication rates between the groups. The introduction of the RA TKA system was associated with a learning curve for operative time of 8.7 cases. Operative times between the RA TKA and conventional TKA group were similar. The short learning curve implies this RA TKA system can be adopted relatively quickly into a surgical team with minimal risks to patients

Background. Intraoperative balancing of total knee arthroplasty (TKA) can be accomplished by either more prevalent but less predictable soft tissue releases, implant realignment through adjustments of bone resection or a combination of both. Robotic TKA allows for quantifiable precision performing bone resections for implant realignment within acceptable final component and limb alignments. Objective. To provide a direct comparison of patient reported outcomes between implant realignment and traditional ligamentous release for soft tissue balancing in TKA. Methods. IRB approved retrospective single surgeon cohort study of prospectively collected operative and clinical data of consecutive patients that underwent TKA with a single radius design utilizing kinematic sensors to assess final balance with or without robotic assistance allowing for a minimum of 12 months clinical follow up. Operative reports were reviewed to characterize the balancing strategy. In surgical cases using robotic assistance, pre-operative plan changes that altered implant placement were included in the implant realignment group. Any patient that underwent both implant realignment and soft tissue releases was analyzed separately. Kinematic sensor data was utilized to quantify ultimate balance to assure that each cohort had equivalent balance. Patient reported outcome data consisting of Knee Society- Knee Scores (KS-KS), Knee Society- Function Scores (KS-FS), and Forgotten Joint Scores (FJS) were prospectively collected during clinical follow up. Results. 182 TKA were included in the study. 3-Month clinical follow up was available for 174/182 knees (91%), 1-Year clinical follow up was available for 167/182 knees (92%) and kinematic sensor data was available for 169/182 knees (93%). Kinetic sensor data showed that on average all of the balancing subgroups achieved clinically equivalent balance. Use of robotic-arm assistance provided the tools and confidence to decrease from ligament release only in 40.8% of non-robotic cases to 3.8% in the robotic group, and the use of component realignment alone increased from 23.7% in the non-robotic cases to 48.1% in the robotic TKA group. KS-KS, KS-FS and FJS scores showed improvements in outcomes at both the 3-month and 1-year time points in the implant realignment cohort compared to the ligamentous release cohort. KS-KS, KS-FS, and FJS at 1-year were 1.6, 7.6, and 17.2 points higher respectively. While none of the comparisons reached statistical significance, KS-FS at 1 year showed a statistically and clinically significant difference (MCID 6.1–6.4) increase of 7.7 points in the implant realignment cohort compared to the ligamentous cohort. The 1-year trend can be further explained by the outperformance (MCID increase of 6.4 points) of the implant realignment robotic cohort at 1-year compared to the non-robotic ligamentous cohort. Conclusions. Directly comparing TKA patients balanced with implant realignment alone versus ligamentous release alone versus combined technique, a trend toward clinical improvement above a minimally clinical significant difference in KS-FS scores benefiting the implant realignment technique was seen at both 3-months and 1-year post-operatively. We hypothesize that the benefit of implant realignment is achieved through decreased soft tissue trauma as well as potentially greater predictability and sustainability of soft tissue balance than with soft tissue releases alone

Robotic arm-assisted total knee replacement is performed as a semi-active system in which haptic guidance is used to precisely position and align components. This is based on pre-operative planning based on CT imaging and can be modified as needed throughout the procedure. This technology, as shown with unicompartmental arthroplasty, is more accurate than conventional and even computer navigated instrumentation and will decrease variability. The knee can be planned to a neutral mechanical alignment. Intra-operatively, the computer will demonstrate compartment gap measurements to assist with soft tissue balancing. Alternatively, limb and component alignment can be accurately adjusted several degrees off the neutral axis to balance the knee and avoid or minimise soft tissue releases. This allows a more constitutional alignment within the alignment parameters accepted by the surgeon. This technique was utilised commonly in the first 60 robotic total knee replacements performed. We will now have the ability to collect accurate component positioning, alignment, and soft tissue balance data that can be correlated to outcomes of total knee replacements

Introduction. Robotic systems have been used in TKA to add precision, although few studies have evaluated clinical outcomes. We report on early clinical results evaluating patient reported outcomes (PROs) on a series of robotic-assisted TKA (RAS-TKA) patients, and compare scores to those reported in the literature. Methods. We prospectively consented and enrolled 106 patients undergoing RAS-TKA by a single surgeon performing a measured-resection femur-first technique using a miniature bone-mounted robotic system. Patients completed a KOOS, New Knee Society Score (2011 KSS) and a Veterans RAND-12 (VR-12) pre-operatively and at 3, 6 and 12 months (M) post- operatively. At the time of publication 104, 101, and 78 patients had completed 3M, 6M, and 12M PROs, respectively. Changes in the five KOOS subscales (Pain, Symptoms, Activities of Daily Living (ADL), Sport and recreation function (Sport/Rec) and Knee-related Quality of Life (QOL)) were compared to available literature data from FORCE – TJR, a large, prospective, national cohort of TJR patients enrolled from diverse high-volume centers and community orthopaedic practices in the U.S, as well as to individual studies reporting on conventional (CON-TKA) and computer-assisted (CAS- TKA) at 3M, and on conventional TKA at 6M. The 2011 KSS is a validated method for quantifying patient's expectations and satisfaction with their TKA procedure. Improvements in the 2011 KSS were compared with literature data at 6M post-operatively. Results. RAS-TKA PRO's significantly improved at 3, 6, and 12M from pre-operative baseline values. When compared to the FORCE registry cohort data, the improvement in KOOS subscales were generally higher for RAS for pain at 6M, and for pain, ADL, and QOL at 1Y when compared with FORCE 2Y data. Higher improvements were also seen at 3M, except for Sports/Rec, and at 6M for symptoms and QOL when compared with smaller cohort studies. Improvements in 2011 KSS patient satisfaction and functional scores at 6M were 11 and 10 points greater than those reported for conventional TKA. A mean of 31 pts for the Patient Satisfaction score indicates that on average patients were ‘Satisfied’ with their knee function and pain level. Mean rates of dissatisfaction with knee pain level and function were 9.2%, 3.8% and 3.1% at 3, 6, and 12M postoperatively, respectively. A mean of 10pts for the Expectation score post-operatively indicates that on average patients felt their expectations for pain relief, ADL, and leisure/sports/rec activities were between “Just Right” or “Too Low”. Discussion. Early results of RAS-TKA demonstrated significant improvements in pain, function, and QOL from baseline pre-operative values. PROs for robotic TKA also compared favorably with results reported in the literature; however, additional randomized control studies are required to provide more meaningful comparisons with conventional techniques and with other advanced technologies

Total knee arthroplasty is a successful procedure with good long-term results. Studies indicate that 15% – 25% of patients are dissatisfied with their total knee arthroplasty. In addition, return to sports activities is significantly lower than total hip arthroplasty with 34% – 42% of patients reporting decreased sports participation after their total knee arthroplasties. Poor outcomes and failures are often associated with technical errors. These include malalignment and poor ligament balancing. Malalignment has been reported in up to 25% of all revision knee arthroplasties, and instability is responsible for over 20% of failures. Most studies show that proper alignment within 3 degrees is obtained in only 70% – 80% of cases. Navigation has been shown in many studies to improve alignment. In 2015, Graves examined the Australian Joint Registry and found that computer navigated total knee arthroplasty was associated with a reduced revision rate in patients under 65 years of age. Navigation can improve alignment, but does not provide additional benefits of ligament balance. Robotic-assisted surgery can assist in many of the variables that influence outcomes of total knee arthroplasty including: implant positioning, soft tissue balance, lower limb alignment, proper sizing. The data on robotic-assisted unicompartmental arthroplasty is quite promising. Cytech showed that femoral and tibial alignment were both significantly more accurate than manual techniques with three times as many errors with the manually aligned patients. Pearle, et al. compared the cumulative revision rate at two years and showed this rate was significantly lower than data reported in most unicompartmental series, and lower revision rates than both Swedish and Australian registries. He also showed improved satisfaction scores at two years. Pagnano has noted that optimal alignment may require some deviation from mechanically neutral alignment and individualization may be preferred. This is also likely to be a requirement of more customised or bi-cruciate retaining implant designs. The precision of robotic surgery may be necessary to obtain this individualised component alignment. While robotic total knee arthroplasty requires further data to prove its value, more precise alignment and ligament balancing is likely to lead to improved outcomes, as Pearl, et al. and the Australian registry have shown. While it is difficult to predict the future at this time, I believe robotic-assisted total knee arthroplasty is the future and that future begins now

Purpose. Various alignment philosophies for total knee arthroplasty (TKA) have been described, all striving to achieve excellent long-term implant survival and good functional outcomes. In recent years, in search of higher functionality and patient satisfaction, a shift towards more patient-specific alignment is seen. Robotics is the perfect technology to tailor alignment. The purpose of this study was to describe ‘inverse kinematic alignment’ (iKA) technique, and to compare clinical outcomes of patients that underwent robotic-assisted TKA performed by iKA versus adjusted mechanical alignment (aMA). Methods. The authors analysed the records of a consecutive series of patients that received robotic assisted TKA with iKA (n=40) and with aMA (n=40). Oxford Knee Score (OKS) and satisfaction on a visual analogue scale (VAS) were collected at a follow-up of 12 months. Clinical outcomes were assessed according to patient acceptable symptom state (PASS) thresholds, and uni- and multivariable linear regression analyses were performed to determine associations of OKS and satisfaction with 6 variables (age, sex, body mass index (BMI), preoperative hip knee ankle (HKA) angle, preoperative OKS, alignment technique). Results. The iKA and aMA techniques yielded comparable outcome scores (p=0.069), with OKS respectively 44.6±3.5 and 42.2±6.3. VAS Satisfaction was better (p=0.012) with iKA (9.2±0.8) compared to aMA (8.5±1.3). The number of patients that achieved OKS and satisfaction PASS thresholds was significantly higher (p=0.049 and p=0.003, respectively) using iKA (98% and 80%) compared to aMA (85% and 48%). Knees with preoperative varus deformity, achieved significantly (p=0.025) better OKS using iKA (45.4±2.0) compared to aMA (41.4±6.8). Multivariable analyses confirmed better OKS (β=3.1; p=0.007) and satisfaction (β=0.73; p=0.005) with iKA. Conclusions. The results of this study suggest that iKA and aMA grant comparable clinical outcomes at 12-months follow-up, though a greater proportion of knees operated by iKA achieved the PASS thresholds for OKS and satisfaction. Notably. in knees with preoperative varus deformity, iKA yielded significantly better OKS and satisfaction than aMA

Introduction. The purpose of this study was to demonstrate the feasibility of passively collecting objective data from a commercially available smartphone-based care management platform (sbCMP) and robotic assisted total knee arthroplasty (raTKA). Methods. Secondary data analysis was performed using de-identified data from a commercial database that collected metrics from a sbCMP combined with intraoperative data collection from raTKA. Patients were included in this analysis if they underwent unilateral raTKA between July 2020 and February 2021, and were prescribed the sbCMP (n=131). The population consisted of 76 females and 55 males, with a mean age of 64 years (range, 43 – 81). Pre-operative through six-week post-operative data included step counts from the sbCMP, as well as administration of the KOOS JR. Intraoperative data included surgical times, the hip-knee-ankle angle (HKA), and medial and lateral laxity assessments from the robotic assessment. Data are presented using descriptive statistics. Comparisons were performed using a paired samples t-test, or Wilcoxon Signed-rank test, with significance assessed at p<0.05. A minimal detectable change (MDC) in the KOOS JR score was considered ½ standard deviation of the preoperative values. Results. KOOS JR scores improved from a preoperative mean of 51.5 ± 11.5 to a 6-week postoperative mean of 64 ± 10.04 (p<0.001). An MDC of 5.75 units was achieved. Step counts decreased initially and returned to preoperative values by week 6 (Figure 1, p=0.196). When evaluating time requirements from landmarking to completed surgical cuts, the median surgical time was 40.2 minutes (IQR, 29.4 – 52.0). The median absolute deformity for HKA preoperatively was 6.9 degrees (IQR, 4.1 – 10.1) and the final intraoperative median HKA was 0.9 degrees (IQR, 0.1 – 3, p<0.001). There was a difference in medial and lateral joint laxity in flexion and extension at the initial intraoperative evaluation (p<0.01). At the final evaluation there was no difference in medial and lateral joint laxity in extension (p=0.239); however, a slight difference in flexion was noted (p=0.001). Given the median values of 1.2mm (0.8 – 2.4) medially vs. 1.4mm (0.9 – 3) laterally, this difference is not likely clinically relevant. Patients who had <1 mm of medial laxity in flexion had significantly fewer step counts at week 6 post-operatively (p=0.035). There was no difference in KOOS JR scores associated with tightness (p>0.05). Discussion. The use of passively collected objective measures in a commercial database across the episode of care was feasible and demonstrated associations between intraoperative and post-operative metrics. To our knowledge, this is the first integrated data collection and reporting platform to report on these measures in a commercial population. Future research is needed in order to understand the benefit of displaying these metrics, as well as the role of variations in alignment and gap balance on function. Conclusions. Contemporary data platforms may be used to improve the understanding of individual recovery paths through real-time passive data collection throughout the episode of care. For any figures or tables, please contact the authors directly

Introduction. Achieving a balanced joint with neutral alignment is not always possible in total knee arthroplasty (TKA). Intra-operative compromises such as accepting some joint imbalance, non-neutral alignment or soft-tissue release may result in worse patient outcomes, however, it is unclear which compromise will most impact outcome. In this study we investigate the impact of post-operative soft tissue balance and component alignment on postoperative pain. Methods. 135 patients were prospectively enrolled in robot assisted TKA with a digital joint tensioning tool (OMNIBotics with BalanceBot, Corin USA) (57% female; 67.0 ± 8.1 y/o; BMI: 31.9 ± 4.8 kg/m. 2. ). All surgeries were performed with a PCL sacrificing tibia or femur first techniques technique, using CR femoral components and a deep dish tibial insert (APEX, Corin USA). Gap measurements were acquired under load (average 80 N) throughout the range of motion during trialing with the tensioning tool inserted in place of the tibial trial. Component alignment parameters and post-operative joint gaps throughout flexion were recorded. Patients completed 1-year KOOS pain questionnaires. Spearman correlations and Mann-Whitney-U tests were used to investigate continuous and categorical data respectively. All analysis performed in R 3.5.3. Results. Significant correlations were found between KOOS Pain and joint balance (p < 0.05). Joint gap thresholds of an equally balanced or tighter medial compartment in extension, ±1 mm medial laxity compared to the final insert thickness in midflexion, and medio-lateral imbalance < 1.5 mm in flexion generated subgroups with significantly improved pain outcomes (median Δ = 8.3, 5.6 and 2.8 points, respectively). When all joint balance thresholds were satisfied, further improved outcomes resulted (median Δ = 11.2, p = 0.0018) (Figure 1 Left). No significant correlations were identified between femoral coronal (0.8 ± 2.1° valgus) and axial (2.1 ± 2.7° external) or tibiofemoral extension (1.1 ± 2.4° varus) and flexion (2.4 ± 2.8° varus) coronal alignments and KOOS Pain. Neutral and non-neutral femoral (±3° coronal and 0° – 5° external) and tibiofemoral (±3° coronal and −2° − 5° external) subgroups also reported no difference in KOOS pain outcome (Figure 1 Right). Discussion and Conclusion. The gap profiles identified here help build the understanding of joint balance and its relationship with outcome when using a PCL sacrificing deep dish tibial insert. Using a digitally-controlled distraction device, joint gap windows of clinical relevance were identified with statistically improved patient outcomes. By combining joint gap targets, subpopulations were identified with clinically significant improved pain outcomes. Furthermore, small changes in component alignment did not impact 1 yr pain outcomes, indicating soft tissue balance has a greater impact on outcome that alignment in the enrolled population. For any figures or tables, please contact the authors directly

Introduction/Aim. The NAVIO robotic-assisted TKA (RA-TKA) application received FDA clearance in May 2017. This semi-active robotic technique aims to improve the accuracy and precision of total knee arthroplasty. The addition of robotic-assisted technology, however, also introduces another potential source of surgery-related complications. This study evaluates the safety profile of NAVIO RA-TKA. Materials and Methods. Beginning in May 2017, the first 250 patients undergoing NAVIO RA-TKA were included in this study. All intra-operative complications were recorded, including: bleeding; neuro-vascular injury; peri-articular soft tissue injury; extensor mechanism complications; and intra-operative fracture. During the first 90 days following surgery, patients were monitored for any post-operative complications, including: superficial and deep surgical site infection; pin-tract infection; pin site fractures; peri-prosthetic fractures; axial or sagittal joint instability; axial mal-alignment; patello-femoral instability; DVT/PE; re-operation or re-admission due to surgical-related complications. Surgical technique and multi-modality pain management protocol was consistent for all patients in the study. A combined anesthetic technique was employed for all cases, including: low-dose spinal, adductor canal block and general anesthetic. Patients were mobilized per our institution's rapid recovery protocol. Results. No patients were lost to follow-up. During the study period, no intra-operative complications were recorded. Specifically, no complications related to the introduction of the high-speed burr associated with the NAVIO RA-TKA were noted. Within the 90-day follow-up period, there was one case of deep infection. One patient sustained a fall resulting in a peri-prosthetic femoral fracture, that occurred remote from the femoral pin tracts. No cases of axial or sagittal joint instability, axial mal-alignment, patello-femoral instability, pin site infections or fractures; or DVT/PE were identified. Four patients underwent manipulation under anesthesia. No other patients required a re-operation or re-admission due to surgical-related complications. Discussion/Conclusions. The initial experience with the NAVIO robotic assisted total knee arthroplasty has demonstrated excellent safety profile. Relative to known risks associated with total knee arthroplasty, no increased risk of peri-operative complications, re-operation or re-admission for surgical related complications was identified with the introduction of the NAVIO RA-TKA

Recently, axial radiography has received attention for the assessment of distal femur rotational alignment, and satisfactory results have been as compared with the CT method. The purpose of this study was to assess rotational alignment of the femoral component in knee flexion by axial radiography and to compare flexion stabilities achieved by navigational and robotic total knee arthroplasty (TKA). In addition, the authors also evaluated the effects of flexion stability on functional outcomes in these two groups. Sixty-four patients that underwent TKA for knee osteoarthritis with a minimum of follow-up of 1 year constituted the study cohort. Patients in the navigational group (N = 32) underwent TKA using the gap balancing technique and patients in the robotic group (N = 32) underwent TKA using the measured resection technique. To assess flexion stability using axial radiography a novel technique designed by the authors was used. Rotations of femoral components and mediolateral gaps in the neutral position on flexion radiographs was measured and compared. Valgus and varus stabilities under valgus-varus stress loading, and total flexion stabilities (defined as the sum of valgus and varus stability) were also compared, as were clinical outcomes at final follow up visits. A significant difference was found between the navigation and robotic groups for mean external rotation of the femoral component (2.1° and 0.4°, respectively; p = 0.003). Mean mediolateral gap in neutral at 90° flexion position was 0.17° in the navigation group and 0.07° in the robotic group (p = 0.126), and mean total stability was 7.82° in the robotic group and 8.10° in the navigation group (p = 0.35). Clinically, no significant intergroup difference was found in terms of ranges of motion, HSS scores, KS scores, or WOMAC scores. Both navigational and robotic techniques provide excellent clinical and flexion stability results. Furthermore, axial radiography was found to provide a useful, straightforward means of detecting rotational alignment, flexion gaps, and flexion stability

Introduction. Soft tissue releases are often required to correct deformity and achieve gap balance in total knee arthroplasty (TKA). However, the process of releasing soft tissues can be subjective and highly variable and is often perceived as an ‘art’ in TKA surgery. Releasing soft tissues also increases the risk of iatrogenic injury and may be detrimental to the mechanically sensitive afferent nerve fibers which participate in the regulation of knee joint stability. Measured resection TKA approaches typically rely on making bone cuts based off of generic alignment strategies and then releasing soft tissue afterwards to balance gaps. Conversely, gap-balancing techniques allow for pre-emptive adjustment of bone resections to achieve knee balance thereby potentially reducing the amount of ligament releases required. No study to our knowledge has compared the rates of soft tissue release in these two techniques, however. The objective of this study was, therefore, to compare the rates of soft tissue releases required to achieve a balanced knee in tibial-first gap-balancing versus femur-first measured-resection techniques in robotic assisted TKA, and to compare with release rates reported in the literature for conventional, measured resection TKA [1]. Methods. The number and type of soft tissue releases were documented and reviewed in 615 robotic-assisted gap-balancing and 76 robotic-assisted measured-resection TKAs as part of a multicenter study. In the robotic-assisted gap balancing group, a robotic tensioner was inserted into the knee after the tibial resection and the soft tissue envelope was characterized throughout flexion under computer-controlled tension (fig-1). Femoral bone resections were then planned using predictive ligament balance gap profiles throughout the range of motion (fig-2), and executed with a miniature robotic cutting-guide. Soft tissue releases were stratified as a function of the coronal deformity relative to the mechanical axis (varus knees: >1° varus; valgus knees: >1°). Rates of releases were compared between the two groups and to the literature data using the Fischer's exact test. Results. The overall rate of soft tissue release was significantly lower in the robotic gap-balancing group, with 31% of knees requiring one or more releases versus 50% (p=0.001) in the robotic measured resection group and 66% (p<0.001) for conventional measured resection (table-1) [1]. When comparing as a function of coronal deformity, the difference in release rates for robotic gap-balancing was significant when compared to the conventional TKA literature data (p<0.0001) for all deformity categories, but only for varus and valgus deformities for robotic measured resection with the numbers available (varus: 33% vs 50%, p=0.010; neutral 11% vs 50%, p=0.088, valgus 27% vs 53%, p=0.048). Discussion. Robotic-assisted tibial-first gap-balancing techniques allow surgeons to plan and adjust femoral resections to achieve a desired gap balance throughout motion, prior to making any femoral resections. Thus, gap balance can be achieved through adjustment of bone resections, which is accurate to 1mm/degree with robotics, rather than through manual releasing soft tissues which is subjective and less precise. These results demonstrated that the overall rate of soft tissue release is reduced when performing TKA with predictive gap-balancing and a robotic tensioning system. For any figures or tables, please contact authors directly

Background. Manually instrumented knee arthroplasty is associated with variability in implant and limb alignment and ligament balance. When malalignment, patellar maltracking, soft tissue impingement or ligament instability result, this can lead to decreased patient satisfaction and early failure. Robotic technology was introduced to improve surgical planning and execution. Haptic robotic-arm assisted total knee arthroplasty (TKA) leverages three-dimensional planning, optical navigation, dynamic intraoperative assessment of soft tissue laxity, and guided bone preparation utilizing a power saw constrained within haptic boundaries by the robotic arm. This technology became clinically available for TKA in 2016. We report our early experience with adoption of this technique. Methods. A retrospective chart review compared data from the first 120 robotic-arm assisted TKAs performed December 2016 through July 2018 to the last 120 manually instrumented TKAs performed May 2015 to January 2017, prior to introduction of the robotic technique. Level of articular constraint selected, surgical time, complications, hemoglobin drop, length of stay and discharge disposition were collected from the hospital record. Knee Society Scores (KSS) and range of motion (were derived from office records of visits preoperatively and at 2-weeks, 7-weeks and 3-month post-op. Manipulations under anesthesia and any reoperations were recorded. Results. Less articular constraint was used to achieve balance in the robotic group, with a higher incidence of cruciate retaining retention (92% vs. 55%, p < 0.01) and a trend towards lower use of varus-valgus constrained articulations (5% vs. 11%, p = 0.068). Robotic surgery increased mean operative time by 22 minutes (p < 0.001). Operative time improved by 26 minutes from the first 10 robotic cases to the last 10 robotic cases. The robotic group had a lower hospital length of stay (2.7 vs. 3.4 days, p < 0.001). Discharge home was not significantly different between robotic and manual groups (89% vs. 83%, p = 0.2). Postoperative Knee Society scores were similar between groups at each postoperative time interval. Robotic-arm assisted TKA patients demonstrated lower mean flexion contracture at 2-weeks (1.8 vs. 3.3 degrees, p < 0.01), 7-weeks (1.0 vs. 1.8 degrees, p <0.01), and 3-months (0.6 vs 2.1 degrees, p = 0.02) post-surgery, but these differences were small. Mean flexion did not differ between groups at 3-month follow-up, but motion was achieved with a significantly lower rate of manipulation under anesthesia in the robotic group (4% vs 17%, p = 0.013). Conclusion. Preliminary findings demonstrate robotic-arm assisted TKA is safe and efficacious with outcomes comparable, if not superior, to that of manually instrumented TKA. Keywords. total knee arthroplasty, robotic arm-assisted total knee arthroplasty. For any figures or tables, please contact authors directly

Introduction. Component position and overall limb alignment following Total Knee Arthroplasty (TKA) have been shown to influence device survivorship and clinical outcomes. However current methods for measuring post-operative alignment through 2D radiographs and CTs may be prone to inaccuracies due to variations in patient positioning, and certain anatomical configurations such as rotation and flexion contractures. The purpose of this paper is to develop a new vector based method for overall limb alignment and component position measurements using CT. The technique utilizes a new mathematical model to calculate prosthesis alignment from the coordinates of anatomical landmarks. The hypothesis is that the proposed technique demonstrated good accuracy to surgical plan, as well as low intra and inter-observer variability. Methods. This study received institutional review board approval. A total of 30 patients who underwent robotic assisted TKA (RATKA) at four different sites between March 2017 and January 2018 were enrolled in this prospective, multicenter, non-randomized clinical study. CT scans were performed prior to and 4–6 weeks post-operatively. Each subject was positioned headfirst supine with the legs in a neutral position and the knees at full extension. Three separate CT scans were performed at the anatomical location of the hip, knee, and ankle joint. Hip, knee, and ankle images were viewed in 3D software and the following vertices were generated using anatomical landmarks: Hip Center (HC), Medial Epicondyle Sulcus (MES), Lateral Epicondyle (LE), Femur Center (FC), Tibia Center (TC), Medial Malleolus (MM), Lateral Malleolus (LM), Femur Component Superior (FCS), Femur Component Inferior (FCI), Coronal Femoral Lateral (CFL), Coronal Femoral Medial (CFM), Coronal Tibia Lateral (CTL), and Coronal Tibia Medial (CTM). Limb alignment and component positions were calculated from these vertices using a new mathematical model. The measurements were compared to the surgeons’ operative plan and component targeted positions for accuracy analysis. Two analysts performed the same measurements separately for inter-observer variability analysis. One of the two analysts repeated the measurements at least 30 days apart to assess intra-observer variability. Correlation analysis was performed on the intra-observer analysis, while Bland Altman analysis was performed on the inter-observer analysis. Results. Average measurement errors of overall limb alignments, femoral and tibial component position were less than 1 degree. Bland Altman plots for inter-observer analysis demonstrate great reproducibility in limb and component alignment measurements between surgeons with no bias. Correlation plots for intra-observer analysis demonstrate low variability with slopes ranging between 0.86 to 1.00 and R value greater than 0.88. Discussion. The proposed method demonstrated good accuracy to plan and low intra- and inter observer variability. This technique may be considered for assessing component position accuracy with post-operative CTs. Further studies are needed to investigate the robustness of the method in a larger cohort. For any figures or tables, please contact authors directly

Introduction. Active robotics for total knee Arthroplasty (TKA) uses a CAD-CAM approach to plan the correct size and placement of implants and to surgically achieve planned limb alignment. The TSolution One Total Knee Application (THINK Surgical Inc., Fremont, CA) is an open-implant platform, CT-based active robotic surgical system. A multi-center, prospective, non-randomized clinical trial was performed to evaluate safety and effectiveness of robotic-assisted TKA using the TSolution One Total Knee Application. This report details the findings from the IDE. Methods. Patients had to be ≥ 21 years old with BMI ≤ 40, Kellgren-Lawrence Grade ≥ 3, coronal deformity ≤ 20°, and sagital flexion contracture ≤ 15° to participate. In addition to monitoring all adverse events (AE), a pre-defined list of relevant major AEs (medial collateral ligament injury, extensor mechanism disruption, neural deficit, periprosthetic fracture, patellofemoral dislocation, tibiofemoral dislocation, vascular injury) were specifically identified to evaluate safety. Bleeding complications were also assessed. Malalignment rate, defined as the percentage of patients with more than a ± 3° difference in varus-valgus alignment from the preoperative plan, was used to determine accuracy of the active robotic system. Knee Society Scores (KSS) and Short Form 12 (SF-12) Health Surveys were assessed as clinical outcome measures. Results were compared to published values associated with manual TKA. Results. A total of 115 patients were enrolled at 6 US centers and followed for a maximum of 12 months after surgery. Mean surgical time (incision to close) improved consistently as the technique evolved (first 10 cases = 131.5 min, first 20 cases = 122.4 min), with mean robot time = 45.8 min. The incidence of pre-defined AEs identified was 0%, serving as a measure of safety of the procedure. Outside of the pre-defined list, only one AE was definitely associated with the use of the device; a metal tack was left inside the knee joint but no reoperation was performed. No patients required a blood transfusion. Alignment outside of the ± 3° goal was 11.2% with a difference of 0.5° ± 1.9° (mean ± STD), which represents a 43% statistically significant (posterior probability > 0.95) reduction in malalignment compared to the literature. Mean KSS Functional scores improved from 40.2 at baseline to 65.4 at 3 months, mean KSS Objective scores improved from 46.9 to 71.2, mean KSS Patient Satisfaction scores improved from 14.5 to 30.6, and mean SF-12 Physical Component scores improved from 32.9 to 43.5. Discussion. The TSolution One Total Knee Application is descended from an active robotic system used in >8000 cases outside the United States since 2002. This trial represents the first US based study of this technology for primary TKA. The clinical study demonstrated positive safety outcomes as none of the seven pre-defined AEs were observed and there were no cases requiring transfusion. A positive effectiveness outcome was also demonstrated as the malalignment rate found in this study showed a substantial reduction from the 32% malalignment rate published in the literature for conventional instruments. KSS and SF-12 scores were comparable to other published TKA series. For any figures or tables, please contact authors directly